In recent years, various techniques for controlling a vehicle in accordance with map data that is used in a navigation system is proposed. The map data must have a sufficient accuracy for controlling the vehicle in an appropriate manner. However, currently available map data does not have the sufficient accuracy for a required control.
A couple of the techniques for controlling the vehicle use a trace of a travel of the vehicle stored for controlling the vehicle. The trace of the travel of the vehicle is stored as control information for controlling the vehicle.
For example, Japanese patent document JP-A-2005-91071 discloses a road information study system that improves an accuracy of averaged data when the system compiles road information database for controlling the vehicle based on a collection of data being picked up a sensor on the vehicle. In this system, the road information is detected while the vehicle travel a road, and the road information database is stored in associated with positional information in road map information. Then, the average and standard deviation of the road information database are used to calculate road information selection criteria that ranges around the averaged data. Then, the road information in the range of the selection criteria is adopted as an update information of the road information database. In this manner, the variation of the road information is removed beforehand so as to improve the accuracy of the average of the road information database.
Further, Japanese patent document JP-A-2001-141467 discloses a database modification system that modifies road database having a predetermined set of registered roads. The database modification system in the above disclosure identifies a road that is traveled by the vehicle based on a current position and a node data, and modifies the database based on a travel route data for representing the identified road and travel trace data for representing a trace of a travel of the vehicle. Then, the travel route is divided into plural portions for determining that at least one of a start and an end of the trace of the travel of the vehicle in the divided portion of the travel route is in a straight portion. When none of the start and the end of the trace of the travel of the vehicle is in the straight portion, at least one of the start and the end of the trace is changed.
Furthermore, Japanese patent document JP-A-2005-121707 discloses a road information modification apparatus that matches a road shape of stored road information with a real road shape including information on a drive lane of the road. The road information modification apparatus modifies the stored road information based on a travel trace information of the vehicle that actually traveled a road. The road information modification apparatus modifies the road information on respective drive lanes based on the travel trace information when the stored road information is capable of representing the road shape as an integrated road of bi-directional traffic.
However, the apparatus and the system in the above disclosures only consider a control of the vehicle according to a real shape of the road based on a trace of a travel of the vehicle. That is, in other words, a timing of the vehicle control is not considered in terms of a required accuracy of the control.